Implantable medical devices, for example, electrical leads, typically include fixation features that are designed to hold the device in place at an implant site, within a body of a patient, in order to facilitate the collection of diagnostic information at, or the delivery of therapy to the site. One example of an implantable medical electrical lead 200 that includes fixation features is the Model 3889 quadripolar lead, available from Medtronic, Inc. for Interstim® Therapy, a representation of which is shown in the plan view of FIG. 1A. FIG. 1A illustrates a fixation feature 149 of this prior art lead 200 including a plurality of independent, tined elements or components 14, which are mounted around a body 11 of lead 200 and spaced apart from one another along a length of body 11, just proximal to electrodes 12. The construction of tined components 14 and of lead 200 can be similar to that described in commonly-assigned U.S. Pat. No. 6,999,819.
FIG. 1B is a longitudinal cross-section view through body 11, along a section thereof where tined components 14 are attached. FIG. 1B illustrates body 11 including an elongate conductor coil 113 surrounded by an outer insulation sheath 115, and each individual tined component 14 including a mounting band 145 that encircles sheath 115, being bonded thereto. Each tine 141 extends outward from the corresponding band 145, yet is relatively flexible to bend, for example, per arrow B, when the section of lead body 11 is inserted, per arrow I, into an introducer needle or sheath for the implantation of lead 200. Once the introducer needle/sheath is withdrawn from around fixation feature 149, tines 141 of each tined component 14 extend outward again to hold electrodes 12 of lead 200 in a relatively fixed implant position, for example, to stimulate sacral nerves, as is illustrated in the schematic of FIG. 2 (borrowed from the above-referenced '819 patent). With reference back to FIG. 1A, conductor coil 113 electrically couples each electrode to a corresponding connector contact of a proximal connector terminal 23 of lead 200.
With reference to FIG. 2, tines 141, once released from the constraint of the introducer needle/sheath, extend outward within the subcutaneous tissue and thereby prevent proximal dislodgement of lead 200, for example, per arrow P. It should be noted that the Model 3889/lead 200 is constructed for chronic implantation, but that a similar fixation feature may be employed by medical electrical leads that are intended for temporary implant, for example, to evaluate the efficacy of sacral nerve stimulation, like that described in the commonly-assigned and co-pending patent application entitled TEMPORARY IMPLANTABLE MEDICAL ELECTRICAL LEADS, filed on Apr. 14, 2010 as U.S. Provisional Patent Application No. 61/324,144, filed Apr. 14, 2010, now U.S. patent application Ser. No. 13/084,420, filed Apr. 11, 2011.
Although fixation features, for example, like feature 149, that are known in the art, have been found effective for holding an implanted medical device in place, there is still a need for new fixation components that can facilitate simpler device construction/assembly, for example, in order to reduce cost and/or increase repeatability in the manufacturing of relatively large volumes of the devices. Simpler device constructions can be particularly beneficial for relatively low profile devices that employ relatively small components, like the aforementioned temporary implantable leads.